A survey on modality characteristics, performance evaluation metrics, and security for traditional and wearable biometric systems

Biometric research is directed increasingly toward Wearable Biometric Systems (WBS) for user authentication and identification. However, prior to engaging in WBS research, how their operational dynamics and design considerations differ from those of Traditional Biometric Systems (TBS) must be understood. While the current literature is cognizant of those differences, there is no effective work that summarizes the factors where TBS and WBS differ, namely, their modality characteristics, performance, security, and privacy. To bridge the gap, this article accordingly reviews and compares the key characteristics of modalities, contrasts the metrics used to evaluate system performance, and highlights the divergence in critical vulnerabilities, attacks, and defenses for TBS and WBS. It further discusses how these factors affect the design considerations for WBS, the open challenges, and future directions of research in these areas. In doing so, the article provides a big-picture overview of the important avenues of challenges and potential solutions that researchers entering the field should be aware of. Hence, this survey aims to be a starting point for researchers in comprehending the fundamental differences between TBS and WBS before understanding the core challenges associated with WBS and its design.